Class of amine coinitiators in photoinitiated polymerizations

ABSTRACT

A new class of amines is incorporated into phtopolymerizable systems employing type I or type II photoinitiators. These amines are trialkylamines having a total of 10 to about 36 carbon atoms in the molecule and wherein at least one alkyl group has a chain length of at least 8 carbon atoms. Preferably, one or two of the alkyl groups are methyl or ethyl or one of each. Short chain amines as defined herein provide synergistic results when used with such trialkylamines.

This application is a National filing of PCT/US03/12955, filed Apr. 24,2003, which claims benefit of provisional application 60/375,639, filedApr. 26, 2002.

BACKGROUND

In light cured applications utilizing Type II photoinitiators (hydrogenabstraction), low molecular weight amines are typically incorporated asa coinitiator. These small molecule amines are not always fully reactedand can remain in the final cured matrix, which pose complications suchas residual extractables and leachables.

Using light to cure coatings comes with motivations such asenvironmental compliance, fast cure, improved physical properties andlower applied cost. These motivators translate into benefits of reducedsolvent emissions, increased product speed/productivity, productperformance, efficiency and cost effectiveness. The use of UV-EB hasenjoyed a growth rate of approximately 10% per annum over the lastdecade and equates to an annual industrial usage of about 100,000,000lbs. Nevertheless, some obstacles include cost of products, equipmentcost, poor weatherability, adhesion and curing of thick samples andresidual uncured materials. While many of these issues are successfullybeing addressed, unsolved problems and deterrents still exist.

A UV curable formulation can contain several fundamental components, ofwhich can be monomers, functionalized oligomers, and photoinitiators(free-radical or cationic). Among additional components which can alsobe included are, for example, pigments, dyes, light stabilizers, radicalscavengers and adhesion promoters.

Free-radical photoinitiators are typed into two classes: Type I, thosethat undergo photocleavage to yield free-radicals and Type II, thosethat produce initiating radicals through an abstraction process. Type Iphotoinitiators produce radicals through a unimolecular fragmentation.Examples of these include aromatic carbonyl compounds, such asderivatives of benzoin, benzilketal and acetophenone. One example is2,2-dimethoxy-2-phenylacetophenone (DMPA), the reaction pathways ofwhich are as follows:

Upon irradiation DMPA cleavage occurs by generating the benzyl radicaland a dimethoxy substituted carbon centered radical. The dimethoxyradical rearranges to form a methyl radical and methylbenzoate. Thebenzyl radical can initiate polymerization or abstract hydrogens formingbenzaldehyde. Unreacted residual DMPA and other small molecules remainin the final polymer matrix and can be readily extracted and leached.This makes these coatings unfit for applications that involve contactwith food, notably an emerging application. Residual DMPA can alsofurther react leading to premature degradation of the polymer. Thesematerials then cannot be used for outdoor applications where exposure tointense UV would be expected.

Thus while Type I photoinitiators typically provide high rates ofinitiation, yielding rapid controllable rates of polymerization and fastcuring line speeds, Type I systems are often expensive and can producetoxic by-products.

Type II (abstraction type) photoinitiators are typically aromaticketones, such as thioxanthone and benzophenone derivatives. In thesesystems, a coinitiator must be present in order to produce an initiatingradical. These coinitiators can include amines, alcohols or ethers. Theprocess of producing radicals is either through a hydrogen abstractionor an electron transfer mechanism depending on the coinitiator. Theprimary initiating radical is usually a radical centered on thecoinitiator. In the presence of abstractable hydrogens (such as amine,ether, thiol or alcohol) the reaction produces two radicals. Thereaction pathway may be depicted as follows:

When the hydrogen donor source is an amine, the excited statebenzophenone participates in an electron transfer process forming theradical-anion/radical-cation pair. This is subsequently followed by arapid proton-transfer from a carbon alpha to the nitrogen on the amine(aminyl radical) to the benzophenone radical-anion producing thesemipinacol ketyl type radical and a carbon centered radical on theamine. The semipinacol ketyl type radical is not efficient at initiatingpolymerization, whereas the aminyl radical readily initiatespolymerization. The products from the semipinacol ketyl type radical arestill photoactive and can lead to photosensitivity of the final film.

In light cured applications utilizing Type II photoinitiators (hydrogenabstraction), tertiary amines are typically incorporated as acoinitiator, due to their reactivity with type II photoinitiators. Aminesynergists can be placed in three categories: amine acrylates, amineacrylate adducts, and free-amines (ethanolamines).

Amine acrylates are made by the reaction of an amine and amultifunctional acrylate in such a ratio as to produce an oligomericcompound. Amine acrylates do not blush or discolor sensitive pigments,but are costly, can cause skin burns, have high viscosity, and must beused in the range of 12-20 wt % to be effective.

Amine acrylate adducts are formed from reacting secondary amines with anacrylate monomer. The amount of amine functionality is controlled by theratio of amine to acrylate. The amine acrylate adducts give good cure,do not blush and contribute to overcoming the effects of oxygeninhibition, but discolor sensitive pigments, can cause skin burns, andmust be used in the range of 8-12 wt % to be effective.

Free-amines (ethanolamines), which are low in cost, effective in therange of 4-6 wt %, and give good through cure as well as contribute toovercoming the effects of oxygen inhibition. However, these blush inhigh humidity, discolor sensitive pigments such as rhodamine red andreflex blue in over print varnishes, are extractable, and contribute toodors due to high vapor pressures. Examples of low molecular weightamines typically used as a coinitiators are N-methyl-N,N-diethanolamine,triethanolamine, triethylamine, triisopropanolamine, andN-methyldibutylamine. These small molecule amines are not always fullyreacted and can remain in the final cured matrix, which posecomplications such as residual extractables and leachables.

Accordingly, when forming films using Type II photoinitiators,especially thin films of about 2 mils or less, a need exists for a wayof eliminating or minimizing (i) extractables in the films, (ii)discoloration of the films, and (iii) premature degradation of thefilms, while at the same time achieving rapid cures. It would beespecially advantageous if not only films but other articles as wellcould be fabricated by photopolymerization using Type I or Type IIinitiators, or both, without increasing extractables, blushing,discoloration or degradation of the resultant article or product.

THE INVENTION

Pursuant to this invention, a new class of amines is incorporated intophotopolymerizable systems employing Type I or Type II photoinitiators,or a combination of both such types. In the case of systems based onType II photoinitiators the amines used pursuant to this inventionoffset the deleterious effects of conventional small molecule amineswithout compromising cure speed performance. Indeed, in films of about 2mils or less, super-fast cures can be accomplished eliminating orminimizing (i) extractables in the films, (ii) discoloration of thefilms, and (iii) premature degradation of the films. The amines usedpursuant to this invention also have low extractables, low viscosity,and low use concentrations. In systems based on use of Type Iphotoinitiators, extractables are not increased and moreover, blushing,discoloration and premature degradation of the polymer can be minimizedby use of the amine coinitiators of this invention.

The amines used in the practice of this invention are one or moretrialkylamines each having a total of 10 to about 36 carbon atoms in themolecule and wherein at least one alkyl group has a chain length of atleast 8 carbon atoms. Preferred amines are (A) one or more trialkylamines each having a total of 10 to about 24 carbon atoms in themolecule, and wherein two of the alkyl groups are methyl or ethyl, orone of each, (more preferably both are methyl), and the remaining alkylgroup contains at least 8 carbon atoms (and more preferably is a primaryalkyl group containing in the range of 8 to about 22 carbon atoms), or(B) one or more trialkyl amines each having a total of 17 to about 38carbon atoms in the molecule, and wherein one of the alkyl groups ismethyl or ethyl(preferably methyl), and the other two alkyl groups arethe same or different, and each is a primary alkyl group). Particularlypreferred amines from the cost-effectiveness standpoint areoctyldimethylamine, decyldimethylamine, dodecyldimethylamine,tetradecyldimethylamine, hexadecyldimethylamine, octadecyldimethylamine,didecylmethylamine, and dodecylmethylamine.

Another aspect of this invention is the discovery that certain shortchain amines when used in combination with the above long chaintrialkylamines behave synergistically, or at least provide improvedresults as compared to the long chain trialkylamine in the absence ofthe short chain amine. For example, the combination of a short chainamine in the form of, e.g.,N-[3-(dimethylamino)propyl]-N,N′,N′-trimethyl-1,3-propanediamine(Polycat 77; Air Products, Inc.), or2,2′-oxybis[N,N-dimethylethanamine](DABCO BL-19; Air Products, Inc.), orpreferably N,N-dimethyl-4-morpholineethanamine (DABCO XDM; Air Products,Inc.), when used in combination with the above long chain trialkylaminesand 2-hydroxy-2-methyl-1-phenylpropane-1-one, provide synergisticresults. N,N-dimethyl-4-morpholineethanamine, when used in combinationwith dodecyldimethylamine and 2-hydroxy-2-methyl-1-phenylpropane-1-one,has been shown to be effective at a lower percentage as compared tomethyldiethanolamine.

The “short chain amines” are tertiary amino compounds containing atleast two electronegative atoms in the molecule, at least one of whichis a tertiary nitrogen atom and another of which is an oxygen atom or atertiary nitrogen atom, and wherein the electronegative atoms are bondedonly to short chain alkyl or alkylene groups (e.g., C₁₋₃ alkyl oralkylene groups), and wherein the compound has a total of at least 4 andpreferably at least 6 abstractable hydrogen atoms in positions alpha toat least some of the electronegative atoms in the compound. Toillustrate,N-[3-(dimethylamino)propyl]-N,N′,N′-trimethyl-1,3-propanediamine hasthree electronegative atoms and a total of 9 abstractable hydrogen atomsin the molecule. 2,2′-Oxybis[N,N-dimethylethanamine] has threeelectronegative atoms and a total of 8 abstractable hydrogen atoms inthe molecule. N,N-dimethyl-2-morpholinoethanamine has twoelectronegative atoms and a total of 8 abstractable hydrogen atoms inthe molecule. N-Hydroxyethylmorpholine has two electronegative atoms anda total of 6 abstractable hydrogen atoms in the molecule. A short chainamine having the requisite number of abstractable hydrogen atoms willcause polymerization to occur when used with benzophenone in a mixturewith epoxyacrylate diluted with tripropylene glycol diacrylate in a35:65 wt ratio on exposure of the mixture UW light at 254 nonometers.The forgoing illustrative short chain amines make clear that the shortchain alkylene groups can be part of a non-cyclic compound or of acyclic compound. Thus for example in N-[3-(dimethylamino)propyl]-N,N′,N′-trimethyl-1,3-propanediamine, the alkylene group (the propane moiety)is in a non-cyclic compound. In contrast, in N-hydroxyethylmorpholinethere are two alkylene (ethylene) groups in the morpholine moiety, whichgroups form a cyclic morpholine ring with an oxygen atom and a nitrogenatom, as well as an open chain alkylene group (the ethyl moiety in theN-hydroxyethyl group).

Among the various types of suitable short chain tertiary amino compoundsare compounds represented by the formula:R—(CH₂)_(n)—NR¹R²where

-   A) R is (i) a dialkylamino group in which each alkyl is,    independently, a C₁₋₃ primary alkyl group; (ii) an    N-alkylpiperazinyl group in which the alkyl is a C₁₋₃ primary alkyl    group, or (iii) a morpholino group;    -   R¹ is a dialkylamino group in which each alkyl is,        independently, a C₁₋₃ primary alkyl group;    -   R² is (i) a dialkylamino group in which each alkyl is,        independently, a C₁₋₃ primary alkyl group; (ii) an alkyleneamino        group in which alkylene is a C₁₋₃ alkylene group and the amino        is a dialkylamino group in which each alkyl is, independently, a        C₁₋₃ primary alkyl group; (iii) an alkyleneaminoalkyleneamino        group (—R—N(R)—R—NR₂) in which each alkylene is, independently,        a C₁₋₃ alkylene group, the amino between the alkylenes is a C₁₋₃        primary alkylamino group, and the other amino is a dialkylamino        group in which each alkyl is, independently, a C₁₋₃ primary        alkyl group; (iv) an alkyleneoxyalkyleneamino group (—R—O—R—NR₂)        in which each alkylene is, independently, a C₁₋₃ alkylene group,        and the amino is a dialkylamino group in which each alkyl is,        independently, a C₁₋₃ primary alkyl group; or (v) an        alkyleneoxyalkyleneoxyalkyleneamino group (—R—O—R—O—R—NR₂) in        which each alkylene is, independently, a C₁₋₃ alkylene group,        and the amino is a dialkylamino group in which each alkyl is,        independently, a C₁₋₃ primary alkyl group;        or where-   B) R is (i) a dialkylamino group in which each alkyl is,    independently, a C₁₋₃ primary alkyl group; (ii) an    N-alkylpiperazinyl group in which the alkyl is a C₁₋₃ primary alkyl    group, or (iii) a morpholino group; and R¹ and R² taken together    is (i) an N-alkylpiperazinyl group in which the alkyl is a C₁₋₃    primary alkyl group, or (ii) a morpholino group.

In addition to the above, many other types of short chain amines can beused pursuant to this invention. In general, the compound will typicallyconsist of one or more tertiary amino groups, one or more ether oxygenatoms, and/or one or two hydroxyl groups linked to each other by C₁₋₃aklylene groups, such that there are at least two tertiary amino groupsor at least one tertiary amino group and at least one ether oxygen atomor at least one hydroxyl group linked together in this fashion, and suchthat the compound has a total of at least 4 and preferably at least 6abstractable hydrogen atoms in positions alpha to at least some of theelectronegative atoms in the compound. The tertiary amino group(s) whennot part of a cycloaliphatic ring system are di(C₁₋₃ alkyl)amino ormono(C₁₋₃ alkyl)amino group(s) depending on whether the tertiary aminogroup is a terminal group or an internal group.

A few non-limiting examples of suitable short chain amines includeN,N,N′-trimethyl-1,2-ethanediamine,N,N,N′,N′-tetramethyl-1,2-ethanediamine,N,N,N′-trimethyl-1,3-propanediamine,N,N,N′,N′-tetramethyl-1,3-propanediamine,N-[2-(dimethylamino)ethyl]-N,N′,N′-trimethyl-1,2-ethanediamine,N-[3-(dimethylamino)propyl]-N,N′,N′-trimethyl-1,3-propanediamine,1,4-dimethylpiperazine, 2,2′-oxybis[N,N-dimethylethanamine],3,3′-oxybis[N,N-dimethylpropanamine],4-[2-(dimethylamino)ethyl]morpholine (a.k.a.N,N-dimethyl-2-morpholinoethanamine),4-[3-(dimethylamino)propyl]morpholine, and the homologs of the foregoingamines in which some or all of the methyl groups are replaced by ethylor propylgroups, triethylenediaamine,4,4′-(oxydi-2,1-ethanediyl)bismorpholine, N-hydroxyethylmorpholine, andN-hydroxypropylmorpholine.

In the photopolymerization of monomer or oligomer, films having athickness of about 2 mils or less, such as in the manufacture ofthinly-coated papers or thin high grade card or paperboard stock for usein magazine covers, brochures, corporate annual reports, folders, andthe like in coating systems operating at high linear speeds, exposuretimes must be extremely short. Such thin photopolymerizable monomer oroligomer coating films are typically applied to paper webs travelling atspeeds of about 10 feet per second and thus the photopolymerizationexposure time of such coated webs travelling at such speeds can be inthe range of as little as about 0.005 to 0.02 second. Thus the aminecoinitiators used pursuant to this invention must function extremelyrapidly while at the same time becoming fixed within the polymerizedcoating without discoloration and without undergoing or causing othertypes of degradation within the thin film.

An advantageous feature of such concurrent production and in situapplication or bonding of such thin photopolymerized coatings on atravelling paper or thin paperboard or card stock is that no otheroperations such as washing or drying are required. Indeed, it ispreferable to conduct the concurrent production and in situ applicationor bonding of not only such thin photopolymerized coatings on atravelling paper or thin paperboard or card stock, but also theproduction of other articles, coatings, or laminates without use ofwashing or drying steps. In short the finished articles of thisinvention are produced with a minimum of steps. All that is required isto place the photopolymerizable composition in the proper place andconfiguration to be photopolymerized and expose the resultant article tosufficient radiation to effect the in situ photopolymerization. Printedmatter, decorations, or the like may thereafter be applied to thephotopolymerized article, coating, or laminate using conventionaltechniques, if desired.

The photopolymerized compositions of this invention can themselvesconstitute photopolymerizable inks or coatings applied as printed,decorative, or pictorial matter on a substrate and then photopolymerizedin place. In this embodiment of the invention the photopolymerizablecomposition will include one or more pigments, dyes, or othercolor-producing substances so that permanent printed matter is formedupon exposure of the resultant article to radiation to effectphotopolymerization.

Photopolymerizable monomers for use in the practice of this inventioninclude acrylates, methacrylates, and the like. Non-limiting examples ofsuch acrylate and methacrylate monomers and oligomers include methylacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butylacrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, lauryl acrylate, lauryl methacrylate, cyclohexyl acrylate,cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate,hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminopropylacrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate,diethylaminopropyl methacrylate, and the like, as well as mixtures ofany two or more thereof.

Polyfunctional monomers and oligomers, i.e., compounds or oligomershaving more than one alpha-beta-ethylenic site of unsaturation, can alsobe used in the practice of this invention. Non-limiting examples of suchsubstances include ethylene glycol diacrylate, ethylene glycoldimethacrylate, 1,4-butanediol diacrylate, 1,4-butanedioldimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanedioldimethacrylate, diethylene glycol diacrylate, diethylene glycoldimethacrylate, dipropylene glycol diacrylate, dipropylene glycoldimethacrylate, tripropylene glycol diacrylate, tripropylene glycoldimethacrylate, trimethylolpropane triacrylate, trimethylolpropanetrimethacrylate, glycerol diacrylate, glycerol dimethacrylate, aliphaticurethane diacrylate, aliphatic urethane dimethacrylate, aliphaticurethane triacrylate, aliphatic urethane hexaacrylate, aromatic urethanediacrylate, aromatic urethane dimethacrylate, aromatic urethanetriacrylate, polyethylene glycol (400) diacrylate, polyethylene glycol(400)dimethacrylate, polyethylene glycol (600) diacrylate, polyethyleneglycol (600)dimethacrylate, ethoxylated neopentylglycol diacrylate,ethoxylated neopentylglycol dimethacrylate, propoxylated neopentylglycol diacrylate, propoxylated neopentyl glycol dimethacrylate, highlyethoxylated trimethylolpropane triacrylate, highly ethoxylatedtrimethylolpropane trimethacrylate, ethoxylated bisphenol A diacrylate,ethoxylated bisphenol A dimethacrylate, erythritol tetraacrylate,erythritol tetramethacrylate, amino-modified epoxy diacrylate, epoxynovolac triacrylate, divinylbenzene, 1,3-diisopropenylbenzene, polyestertriacrylate, polyester tetraacrylate, polyester hexaacrylate, anddiluted acrylic acrylate oligomers such as Ebecryl® 740-40TP, Ebecryl®745, Ebecryl® 754, Ebecryl® 1701, Ebecryl® 1701-TP20, and Ebecryl® 1710(all from UCB Chemicals Corporation), and the like, as well as mixturesof any two or more thereof.

If desired, alpha,beta-ethylenically unsaturated carboxylic acids can beused in conjunction with acrylate and/or methacrylate monomers,typically for the purpose of providing improved adhesion to certainsubstrates. Examples of such acids include methacrylic acid, acrylicacid, itaconic acid, maleic acid, beta-carboxyethyl acrylate,beta-carboxyethyl methacrylate, and the like, as well as mixtures of anytwo or more thereof. Preferred composition of this invention are,however, devoid of such carboxylic acids except as may be present asimpurities or as residuals from manufacture.

Preferred photopolymerizable monomers for use in the practice of thisinvention include tripropylene glycol diacrylate, trimethylol propanetetraacrylate, ethoxylated trimethylol propane tetraacrylate,propoxylated neopentyl glycol diacrylate, hexanediol diacrylate, and thelike, as well as mixtures of any two or more thereof.

Compositions of this invention to be subjected to photopolymerizationtypically contain in the range of about 0.5 to about 85 wt % of one ormore photopolymerizable monomers such as those described above.Preferred compositions of this invention contain in the range of about20 to about 75 wt % of one or more of such photopolymerizable monomers.Selections within these ranges are typically made for effectingadjustments of viscosity to suit the particular application method to beused. More preferred photopolymerizable compositions, especially thoseadapted for use in forming low viscosity web coatings, contain in therange of about 50 to about 70 wt % of one or more such monomers, basedon the weight of the total composition to be subjected tophotopolymerization.

Various photoinitiators can be used in the practice of this invention.Suitable initiators for such use include hydrogen Type I (unimolecularfragmentation type) initiators, such as alpha-diketone compounds ormonoketal derivatives thereof (e.g., diacetyl, benzil, benzyl, ordimethylketal derivatives); acyloins (e.g., benzoin, pivaloin, etc.);acyloin ethers (e.g., benzoin methyl ether, benzoin ethyl ether, benzoinpropyl ether, etc.), acyl phosphine oxides, and other similar Type Iinitiators, including mixtures of any two or more such initiators.Similarly, Type II (abstraction-type) initiators can be used.Non-limiting examples of suitable Type II initiators include xanthone,thioxanthone, 2-chloroxanthone, benzil, benzophenone,4,4′-bis(N,N′-dimethylamino)benzophenone, polynuclear quinones (e.g.,9,10-anthraquinone, 9,10-phenanthrenequinone, 2-ethyl anthraquinone, and1,4-naphthoquinone), or the like, as well as mixtures of any two or morethereof. Preferred Type I initiators include ketals such as benzyldimethyl ketal. Preferred Type II initiators include hydrogen quinonessuch as benzoquinone and 2-ethyl anthraquinone. Mixtures of Type I andType II initiators can also be used. The initiator or mixture ofinitiators is typically added in an amount of 0.01 to 10 parts byweight, preferably 0.05 to 5 parts by weight, per 100 parts by weight ofthe monomer(s) to be photopolymerized.

In effecting photopolymerization pursuant to this invention eithercoherent or non-coherent radiation can be employed. Various sources ofsuch radiation can be employed, such as an ion gas laser (e.g., an argonion laser, a krypton laser, a helium:cadmium laser, or the like), asolid state laser (e.g., a frequency-doubled Nd:YAG laser), asemiconductor diode laser, an arc lamp (e.g., a medium pressure mercurylamp, a Xenon lamp, or a carbon arc lamp), and like radiation sources.Exposure sources capable of providing ultraviolet and visible wavelengthradiation (with wavelengths typically falling in the range of 300-700nm) can also be used for the practice of the present invention.Preferred wavelengths are those which correspond to the spectralsensitivity of the initiator being employed. Preferred radiation sourcesare gas discharge lamps using vapors of mercury, argon, gallium, or ironsalts and utilizing magnetic, microwave or electronic ballast; suchlamps commonly are medium pressure mercury lamps, or lamps made byFusion Systems (i.e., D, H, and V lamps).

Exposure times can vary depending upon the radiation source, andphotoinitiator(s) being used. For preferred high speed applications suchas in forming thin coatings on paper webs travelling at high linearspeeds, times in the range of about 0.005 to about 0.015 second arepreferred. In photopolymerization operations in which the mixture beingpolymerized is either stationary or moving slowly as on a conveyor belt,longer exposure times (e.g., in the range of about 0.2 to about 0.4second can be used.

Pigments and dyes can be used, and often are preferably used, in thephotopolymerizable compositions of this invention. Non-limiting examplesof pigments and typical amounts used in the formulation includephthalocyanine blue (5 to 20 wt %), titanium dioxide (10 to 30 wt %), orother organic or inorganic pigments employed in the art. Optionally,dyes such as nigrosine black or methylene blue may be used to enhancecolor or tone (1 to 5 wt %).

Light stabilizers are another type of additives which can be, andpreferably are, used in the photopolymerizable compositions of thisinvention. Non-limiting examples of such light stabilizers include2-hydroxybenzophenones such as2,2′-dihydroxy-4,4′-dimethoxylbenzophenone,2-(2-hydroxyphenyl)benzotriazoles such as2-(2′-hydroxyphenyl)benzotriazole, sterically-hindered amines such asbis(2,2,6,6-tetramethyl-4-piperidyl)sebacate orbis(2,2,6,6-tetramethyl-4-piperidyl)succinate, oxamides such as4,4′-dioctyloxyanilide, acrylates such as ethylα-cyano-β,β-diphenylacrylate or methyl α-carbomethoxycinnanamate, andnickel complexes such as the nickel complex of2,2′-thiobis[(1,1,3,3-tetramethylbutyl)phenol. Typically the amount usedwill be in the range of about 0.02 to about 5 wt % depending upon theparticular type of light stabilizer employed.

Still another type of additives which can be used, and in preferredembodiments is used, in forming the photopolymerizable compositions ofthis invention is one or more radical scavengers. Non-limiting examplesof suitable radical scavengers for such use include hydroquinone,hydroquinone methyl ether, p-tert-butylcatechol, quinoid compounds suchas benzoquinone and alkyl-substituted benzoquinones, as well as otherradical scavenger compounds known in the art. Typically these componentswill be used in amounts in the range of about 100 ppm to about 2 percentby weight of the composition.

Adhesion promoters constitute yet another type of additive componentswhich can be used in the formation of the photopolymerizablecompositions of this invention. Such components typically are silanederivatives such as gamma-aminopropyltriethoxysilane (DOW A-1100) andequivalent substituted silane products; acid functionally-substitutedresins; oligomers or monomers, such as partial esters of phosphoricacid, maleic anhydride, or phthalic anhydride, with or without acrylicor methacrylic unsaturation; and dimers and trimers ofacrylic/methacrylic acid. If adhesion promoters are used, the preferredtypes are other than alpha,beta-ethylenically unsaturated carboxylicacids. If and when used, the concentration thereof is determinedemperically by adhesion tests. In general, however, amounts are often inthe range of about 0.5 to about 20 wt %, and in more preferred cases inthe range of about 2 to about 10 wt % of the total weight of thecomposition.

Among preferred photopolymerizable compositions of this invention arethose in which the composition is comprised of:

-   a) at least one photopolymerizable monomer,-   b) at least one photopolymerization initiator,-   c) at least one long chain alkylamine, and additionally at least    one, preferably at least two, more preferably at least three, and    most preferably all four of d) through g) as follows:-   d) at least one pigment,-   e) at least one dye,-   f) at least one light stabilizer,-   g) at least one radical scavenger, and    optionally at least one adhesion promoter which preferably is other    than one or more alpha,beta-ethylenically unsaturated carboxylic    acids. The preferred amounts of these components in these preferred    photopolymerizable compositions are as given above.

There are various ways of conducting photopolymerizations pursuant tothis invention. For example, a photopolymerizable composition of thisinvention can be photopolymerized as a thin coating on a travelling web.Alternatively, the photopolymerizable composition can bephotopolymerized as an a coating or laminate on a substrate. Anothervariant is where the photopolymerizable composition is photopolymerizedas an article or shape while in a mold. In these and other modes ofoperation, the exposure to radiation for effecting photopolymerizationcan be continuous or intermittent.

Various photopolymerized compositions, articles and shapes can beproduced by use of this invention. Thus the photopolymerized end productcan be printed matter on a substrate such as paper, cardboard, orplastic film, etc.; manufactured articles such as handles, knobs,inkstand bases, small trays, rulers, etc.; and coatings or laminates onsubstrates such as plywood, metal sheeting, polymercomposite sheeting,etc. As noted above, thin coated paper and coated card or thinpaperboard stock where the coatings are up to about 2 mils in thicknessconstitute preferred articles produced pursuant to this invention.

Preferred applications for the process technology of this inventioninclude the following:

-   preparation of thin paper coatings (e.g., 3 to 10 microns) over    print or film, applied by gravure, flexo, rod, or offset press;-   use as coatings and/or inks (e.g., 15 to 35 microns) applied by    roller coater or curtain coater over flooring (e.g., vinyl sheet    goods) or wood panels; and-   use as coatings and/or inks (e.g., 10 to 20 microns) applied by flat    bed or rotary screen print for labels and packages.

The following non-limiting Examples illustrate this invention.

For Example 1, long chain alkylamines dodecyldimethylamine (ADMA® 12amine), hexadecyldimethylamine (ADMA® 16 amine), octadecyldimethylamine(ADMA® 18 amine), and didecylmethyl amine (DAMA® 1010 amine) wereobtained from Albemarle Corporation. Benzophenone andN-methyl-N,N-diethanolamine (MDEA) were obtained from Aldrich ChemicalCompany, both were used without further purification. 1,6-Hexanedioldiacrylate (HDDA), dipropylene glycol diacrylate (DPGDA), tripropyleneglycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA) andEbecryl® 4833 aliphatic urethane acrylate were obtained from UCBChemicals Corporation. The latter product as supplied is diluted with10% of N-vinyl-2-pyrrolidone.

Line cure experiments were conducted on a Fusion UV Systems conveyerbelt system with an intensity of 495 mJ cm⁻² from a Fusion D-bulb at 52ft min⁻¹. Samples were applied via a draw-down bar with a thickness of 7wet mils on Q-Panels of cold rolled steel. Samples were then passedunder the UV light on the conveyer and cure determined by thumb twisttest.

EXAMPLE 1

Photo-DSC Experiments

The evaluation of long chain alkylamine coinitiators of this inventionwas performed in comparison to MDEA incorporated as a coinitiator. Thesephoto-DSC experiments were performed on a Perkin-Elmer DSC 7 modified toincorporate a medium pressure mercury lamp from Ace Glass. The light ispassed through the DSC sample head through two quartz windows to allowfor the irradiation onto the sample and reference cells. The intensitywas 30 mW cm⁻². 2 μL samples were introduced into specially crimpedaluminum DSC pans with thicknesses in the range of 180-250 μm. Photo-DSCexotherms were acquired by Perkin-Elmer Pyris software and furthermanipulation of data and plotting was performed using standardspreadsheet programs. Representative photo-DSC data for HDDAformulations initiated by benzophenone in the presence of an aminesynergist are summarized in Tables 1 and 2. Light intensity in the runsin Table I was 67.2 mW/cm² at full arc under N₂ purge. It was determinedby photo-DSC that the three long chain alkyldimethylamines performedefficiently when incorporated as an amine synergist compared to 1.0% byweight of N-methyl-N,N-diethanolamine (MDEA) (8.4×10⁻² M) on an equalmolar basis, each with 1.42% by weight of benzophenone (BP) to initiatethe polymerization of 1,6-hexanediol diacrylate (HDDA). As shown inTable 1, the resultant polymerization exotherm data on the three longchain alkyldimethylamines with benzophenone initiator are comparable tothe exotherm obtained when using MDEA with benzophenone. Table 2compares the data on initiation of HDDA polymerization when usingdidecylmethyl amine (DAMA® 1010 amine) in place of MDEA on an equalmolar basis. In these runs the DAMA 1010 amine concentration was set tobe equal to 1.0% by weight of MDEA (8.4×10⁻² M), and the light intensitywas 1.43 mW cm⁻² in N₂ at 365 nm. The polymerization exotherm shows thatthe combination of DAMA® 1010 amine with benzophenone gives a comparableexotherm to that obtained using benzophenone and MDEA.

TABLE 1 Sample Average Photo-DSC Exotherm (mW) BP/MDEA 70 BP/ADMA 16amine 71 BP/ADMA 12 amine 67 BP/ADMA 18 amine 65

TABLE 2 Sample Average Photo-DSC Exotherm (mW) BP/MDEA 24 BP/DAMA 1010amine 36

EXAMPLE 2

Synergistic Amine Blends

As noted earlier, certain short chain amines have been shown to providesynergistic results in blends of this invention. In order to test thesynergistic behavior of certain short chain amines when used incombination with long chain trialkylamines, pre-blends were prepared inthe following way and comparatively tested with a blend of long chainamines only.

Pre-Blend 1:

-   70% Dodecyldimethylamine (ADMA® 12 amine; Albemarle Corporation)-   30% N,N-dimethyl-4-morpholineethanamine (DABCO® XDM; Air Products,    Inc.)    Pre-Blend 2:-   63% Dodecyldimethylamine (ADMA® 12 amine; Albemarle Corporation)-   23% N,N-dimethyl-4-morpholineethanamine (DABCO® XDM; Air Products,    Inc.)-   10% HMPP [2-hydroxy-2-methyl-1-phenylpropane-1-one, a cleavage type    photoinitiator (FirstCure® photoinitiator; Albemarle Corporation)]    Pre-Blend 3:-   90% Dodecyldimethylamine (ADMA® 12 amine; Albemarle Corporation)-   10% HMPP [2-hydroxy-2-methyl-1-phenylpropane-1-one, a cleavage type    photoinitiator (FirstCure® photoinitiator; Albemarle Corporation)]    Base Pre-Blend:-   69.65% Ebecryl 3720TP25 (i.e., an epoxy diacrylate (from UCB    Chemicals))-   21.04% eoTMPTA (i.e., ethoxylated trimethylolpropane triacrylate    also a diluent monomer (from UCB Chemicals))-   8.42% BZP (i.e., benzophenone a hydrogen abstraction photoinitiator    (from Aldrich))-   0.70% DC 57 (i.e., a silicone surfactant for flow/slip properties    (from Dow Corning))-   0.14% FC 430 (i.e., a fluorosurfactant for wetting (from 3M))-   0.05% MEHQ (i.e., the methylether of hydroquinone, a radical    scavenger (from Aldrich))-   TPGDA Tripropyleneglycol diacrylate, a diluent monomer (UCB    Chemicals)

Test blends, labeled X and A-H, which represent combinations ofthepre-blends and TPGDA, along with test results for the MEK Double RubTest for each test blend are shown in Table 3.

TABLE 3 Ingre- dient Test Blends (in gms) X A B C D E F G H Blend 1 0.60.8 1 1.2 Blend 2 — — — — 0.7 0.9 1.1 1.3 Blend 3 1 Base 16.9 16.9 16.916.9 16.9 16.9 16.9 16.9 16.9 Blend TPGDA 2.1 2.5 2.3 2.1 1.9 2.4 2.2 21.8 MEK 20 25 27 27 20 28 26 23 20 Double Rub Test (nos. of rubs)

The curing of formulations employed a Fusion Systems UV Conveyor systemusing an H lamp at 145 fpm speed and dose of 195 mj/cm². Coatings of thetest blends were applied at 5 microns using a wire wound rod over acoated paper chart (i.e., a Leneta chart). The MEK Double Rub Testresults indicate how many “double rubs” it took to break through thecoating material, and show that test blends containing the combinationof long chain amine and short chain amine were typically far superior tothe long chain amine without the presence of a short chain amine. Theadditional presence of HMPP further enhanced the performance of thecombination of long chain amine and short chain amine under the MEKDouble Rub Test.

EXAMPLE 3

A series of performance tests of various photocuring formulations wasperformed. The monomers used, TMPEOTA and TRPGDA, were obtained from UCBChemicals Corporation. Methyldiethanolamine (MDEA), benzophenone (BP)and hydroquinone monomethyl ether (MEHQ) were obtained from Aldrich andused without further purification. DC-57 and FC-430 were obtained fromDow Corning and 3M. All formulations were mixed and allowed to set for24 hours, at which point viscosity was measured. Viscosities of theformulations were performed at 25° C. with a Brookfield LV viscometerusing a #2 spindle at 100 rpm. The formulations were then applied toLeneta charts (Form 5C) using a No. 3 wire wound rod, and cured under aFusion H lamp at 145 fpm (35 mJ cm⁻² of UVC). The formulations are aslisted in Table 4 below; all values given (except viscosity) are inweight percent. Abbreviations are the same as in the preceding Examples.

TABLE 4 Formulation FIRSTCURE AS-1 FIRSTCURE AS-3 Amine Functional AmineFunctional component Synergist Amine Synergist Amine Synergist MDEAAmine Acrylate C Acrylate A Acrylate B Ebercyl 3720-TP25 41.50 41.5039.43 27.67 37.5 39.50 Benzophenone 6.0 6.0 6.0 6.0 6.0 6.0 FIRSTCUREHMPP photoinitiator 0.5 0.5 0.5 0.5 0.5 0.5 DC-57 0.5 0.5 0.5 0.5 0.50.5 FC-430 0.1 0.1 0.1 0.1 0.1 0.1 MEHQ 0.02 0.02 0.02 0.02 0.02 0.02Monomer mix¹ 48.88 49.38 47.95 50.21 45.38 42.38 (TMPEOTA and TRPGDA)Synergist 2.5 2.0 5.5 15.0 10.0 11.0 Total weight 100.0 100.0 100.0100.0 100.0 100.0 Viscosity (cps) 25° C. 165 168 165 170 163 167 ¹Themonomer mixture consisted of approximately 31.0% TMPEOTA and 69.0%TRPGDA, which was used in all formulations for constant monomer cost anddiluency.

In order to determine the effective concentration of the FirstCure ASamine synergist, each AS was incorporated at concentrations from 1.0% to3.0%, with the maximum cure determined by MEK double rubs. Theconcentration of each of the FirstCure AS Series was varied in the testformula (ranging from 1.0% to 3.0%) and results are shown below in Table5. From the results, it was determined that AS-1 was most effective at2.5%, with AS-3 at 2.0%. Thus, these concentrations of AS were chosenfor use as a comparison to the traditional amine synergists.

The final cured films were then evaluated for the following performanceparameters:

-   1. Blush resistance was determined by placing freshly cured draw    downs in a chamber at 95% relative humidity and 95° F. for 24 hours    and visually examined for degree of blushing over the black section    of the chart.-   2. Pigment discoloration was evaluated by making proofs with Reflex    Blue and Rhodamine Red on a Little Joe® press using offset sheet fed    inks applied to SBS board. The proofs were allowed to dry until    unmarred by a thumb twist, then over coated with the UV coatings and    cured at 145 fpm. The freshly cured proofs were placed between glass    plates and the edges were sealed with tape to simulate conditions in    a stack. The plates were then placed in a 50° C. circulating air    oven for 72 hours and rated visually for discoloration; an uncoated    proof was treated similarly as a control.-   3. Methylethylketone (MEK) double rubs were measured 3 min. after    exposure; solvent resistance was determined by ASTM D5402-93.-   4. Yellowness index (YID) was measured using a BYK-Gardner    colorimeter.-   5. Gloss was determined at 60° C. using a BYK-Gardner Tri-Gloss    meter.-   6. Extractions were performed for 10 hours by MEK in a Soxhlet    extractor on films cured at 75 fpm with a Fusion H bulb.    Results of the tests performed are summarized in Table 5.

TABLE 5 FIRSTCURE AS-1 Amine Functional Amine Functional FIRSTCURE AS-3Evaluation Parameter Amine Synergist MDEA Acrylate A Acrylate B AmineSynergist Amime Acrylate C Blush None Severe None Slight None NonePigment discoloration None Severe fade Moderate, Moderate, None Slight,spotty (reflex blue) spotty fade spotty fade discolor and fade Pigmentdiscoloration None Severe fade Moderate, Slight None Moderate fade(rhodamine red) spotty fade spotty fade Solvent resistance 24 24 12 2025 22 (MEK double rubs) Yellowness Index 5.01 5.93 6.02 5.98 4.77 5.82Gloss (60°) 95.7 96.1 95.1 96.5 96.0 95.7 MEK extraction 7.52 7.69 10.3812.62 4.55 5.29 (% wt loss)

Table 5 shows that FIRSTCURE AS-1 amine synergist is comparable to MDEAin every parameter tested, and outperforms MDEA in blush resistance.This performance of FIRSTCURE AS-1 amine synergist was attained usingapproximately half of the loading used for MDEA: only 2.5 wt % FIRSTCUREAS-1 amine synergist was used, versus 5.5 wt % for MDEA. Additionally,FIRSTCURE AS-1 amine synergist performs comparably to, or better than,amine functional acrylates A and B in chemical resistance, pigmentdiscoloration, blush and yellowness. FIRSTCURE AS-1 amine synergistprovides this level of performance at approximately one-fourth of theloading used for the amine functional acrylates A and B: 2.5 wt % forFIRSTCURE AS-1 amine synergist versus 10.0 wt % and 11.0 wt % for aminefunctional acrylates A and B. Since a relatively small percentage ofFIRSTCURE AS-1 amine synergist is required, the remaining percentage canbe substituted with a higher loading of oligomers to give betterproperties, or the monomer can be substituted with a lower cost one toreduce the cost of the final formulation.

Table 5 demonstrates that FIRSTCURE AS-3 amine synergist is comparableto or exceeds the performance of amine acrylate C. In each parameterevaluated, FIRSTCURE AS-3 amine synergist is comparable to or superiorto amine acrylate C. This result was attained was attained at a fractionof the loading of amine acrylateC; 2.0 wt % FIRSTCURE AS-3 aminesynergist versus 15.0 wt % of amine acrylate C. As in the case ofFIRSTCURE AS-1 amine synergist, because a relatively small percentage ofFIRSTCURE AS-3 amine synergist is required, the remaining percentage canbe substituted with a higher loading of oligomers to give betterproperties, and the monomer can be substituted with a lower cost one toreduce the cost of the final formulation.

Compounds referred to by chemical name or formula anywhere in thisdocument, whether referred to in the singular or plural, are identifiedas they exist prior to coming into contact with another substancereferred to by chemical name or chemical type (e.g. another component, asolvent, or etc.). It matters not what preliminary chemical changes, ifany, take place in the resulting mixture or solution, as such changesare the natural result of bringing the specified substances togetherunder the conditions called for pursuant to this disclosure. Also, eventhough the claims may refer to substances in the present tense (e.g.,“comprises”, “is”, etc.), the reference is to the substance as it existsat the time just before it is first contacted, blended or mixed with oneor more other substances in accordance with the present disclosure.

Except as may be expressly otherwise indicated, the article “a” or “an”if and as used herein is not intended to limit, and should not beconstrued as limiting, the description or a claim to a single element towhich the article refers. Rather, the article “a” or “an” if and as usedherein is intended to cover one or more such elements, unless the textexpressly indicates otherwise.

All documents referred to herein are incorporated herein by reference intoto as if fully set forth in this document.

1. A photopolymerizable composition which comprises at least onephotopolymerizable monomer, at least one photopolymerization initiator,and at least one long chain alkylamine which is (a) one or more oftetradecyldimethylamine, hexadecyldimethylamine, andoctadecyldimethylamine, or (b) one or more trialkyl amines each having atotal of 17 to about 38 carbon atoms in the molecule, and wherein one ofthe alkyl groups is methyl, and the other two alkyl groups are the sameor different, and each is a primary alkyl group containing,independently, in the range of 8 to about 22 carbon atoms.
 2. Acomposition as in claim 1 wherein said composition is devoid of anycomponent having one or more free carboxyl groups.
 3. A composition asin claim 1 wherein said photopolymerization initiator is one or moreType I photoinitiators.
 4. A composition as in claim 1 wherein saidphotopolymerization initiator is one or more Type II photoinitiators. 5.A composition as in claim 1 wherein said one or more trialkylamines isdidecylmethylamine.
 6. A composition as in claim 1 further comprising atleast one pigment, dye, or other color-producing substance whereby thecomposition is adapted for forming permanent printed, decorative, orpictorial matter on a substrate when applied thereto andphotopolymerization in place.
 7. A photopolymerized composition orarticle formed from a composition as in claim
 1. 8. A photopolymerizedcomposition or article as in claim 7 wherein said photopolymerizedcomposition or article is an unwashed composition or article.
 9. Aphotopolymerized composition or article as in claim 7 wherein saidphotopolymerized composition or article is in the form of a thin coatingon paper or thin paperboard stock.
 10. A photopolymerized composition orarticle as in claim 9 wherein said photopolymerized composition orarticle is an unwashed composition or article.
 11. A method of forming aphotopolymerized composition or article, which method comprises exposinga photopolymerizable composition as in claim 1 to sufficient radiationto photopolymerize said photopolymerizable composition.
 12. A method asin claim 11 wherein the photopolymerization is effected using coherentradiation.
 13. A method as in claim 11 wherein the photopolymerizationis effected using non-coherent radiation.
 14. A method as in claim 11wherein said photopolymerizable composition is photopolymerized as athin coating on a travelling web.
 15. A method as in claim 11 whereinsaid photopolymerizable composition is photopolymerized as an a coatingor laminate on a substrate.
 16. A method as in claim 11 wherein saidphotopolymerizable composition is photopolymerized as an article orshape while in a mold.
 17. A photopolymerizable composition whichcomprises at least one photopolymerizable monomer, at least onephotopolymerization initiator, and at least one long chain alkylaminehaving (i) one or two methyl or ethyl groups and (ii) at least one alkylgroup having a chain length of at least 8 carbon atoms, and furthercomprising at least one short chain tertiary amino compound containingat least two electronegative atoms in the molecule, at least one ofwhich is a tertiary nitrogen atom and another of which is an oxygen atomor a tertiary nitrogen atom, and wherein the electronegative atoms arebonded only to short chain alkyl groups or to short chain alkylenegroups, and wherein the compound has a total of at least 4 abstractablehydrogen atoms in positions alpha to at least some of theelectronegative atoms in the compound, wherein said compound isN-[3-(dimethylamino)propyl]-N,N′,N′-trimethyl-1,3-propanediamine,2,2′-oxybis[N,N -dimethylethanamine],N,N-dimethyl-4-morpholineethanamine, and wherein said compositionfurther comprises 2-hydroxy-2-methyl-1-phenylpropane-1-one.
 18. Acomposition as in claim 17 wherein said compound has a total of at least6 abstractable hydrogen atoms in positions alpha to at least some of theelectronegative atoms in the compound.
 19. A composition as in claim 17wherein when said compound is N,N-dimethyl-4-morpholineethanamine, saidlong chain amine is dodecyldimethyl amine.
 20. A photopolymerizedcomposition or article formed from a composition as in claim
 17. 21. Amethod of (A) minimizing blushing, discoloration and prematuredegradation of a polymer formed by the photopolymerization of aphotopolymerizable composition which comprises at least onephotopolymerizable monomer, and at least one Type I photopolymerizationinitiator, or (B) eliminating or minimizing extractables, discoloration,and premature degradation of a film having a thickness of 2 mils or lesswhere said film is formed by the photopolymerization of aphotopolymerizable composition which comprises at least onephotopolymerizable monomer, and at least one Type II photopolymerizationinitiator, said method characterized by including in the composition of(A) or of (B) before photopolymerization, at least one long chainalkylamine which is tetradecyldimethylamine, hexadecyldimethylamine,octadecyldimethylamine, or didecylmethylamine.
 22. A method as in claim21 wherein said method is the method of (A).
 23. A method as in claim 21wherein said method is the method of (B).